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Perspectives on new technologies built on anaerobic digestion: insights from Idaho

Published online by Cambridge University Press:  22 April 2025

Jane Kolodinsky*
Affiliation:
Arrowleaf Consulting, Walla Walla, WA, USA
Hannah L. Smith
Affiliation:
Arrowleaf Consulting, Walla Walla, WA, USA
Soren Newman
Affiliation:
Arrowleaf Consulting, Walla Walla, WA, USA
Darin Saul
Affiliation:
Arrowleaf Consulting, Walla Walla, WA, USA
Michelle Tynan
Affiliation:
Arrowleaf Consulting, Walla Walla, WA, USA
*
Corresponding author: Jane Kolodinsky; Email: [email protected]
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Abstract

The adoption of anaerobic digesters (ADs) and technologies stacked with them (AD+) has the potential to offer benefits to dairy producers and the environment. Production of biochar, hydrochar, and bioplastics can reduce greenhouse gas emissions, offer economic benefits to farmers through the sale of value-added products, reduce the need for fertilizer purchases, and promote a circular economy for dairy producers. We use a diffusion of innovations framework augmented to include economic, environmental, social, and regulatory considerations in addition to the operational aspects of the technologies. We conducted interviews with 21 participants representing for-profit, not-for-profit, governmental, and community service agencies in Idaho, the third-largest U.S. dairy state. Semi-structured interviews explored participants’ experiences with and perceptions of how relative advantage, compatibility, complexity, observability, trialability, environmental, economic, and social factors may facilitate or hinder the adoption of AD and three related emerging AD+ technologies. Interviews were analyzed using inductive coding and thematic analysis. Results show that participants were familiar with the need to address dairy manure waste and were interested in the potential benefits to farm revenue and the environment. However, the same factors associated with the relatively low adoption of AD in Idaho may also hinder the adoption of newer AD+ technologies. These include a lack of observability and trialability, installation and maintenance costs, access to technology, uncertain environmental impacts, unrealized economic benefits to dairy producers, and regulatory burden.

Type
Research Paper
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2025. Published by Cambridge University Press

Introduction and background

In the United States, 10% of greenhouse gas (GHG) emissions are attributed to agricultural activities, and the livestock sector is responsible for approximately 11% of these (United States Environmental Protection Agency, 2024). Dairy cows contribute 11% of U.S. methane emissions (Wattiaux et al, Reference Wattiaux2019; Rotz et al., Reference Rotz2021; Wattiaux, Reference Wattiaux2023). Methane has shown about 80 times the global warming potential of carbon dioxide over a 20-year period (Vallero, Reference Vallero and Vallero2019). The U.S. dairy industry has a Net Zero Initiative with an objective to achieve GHG neutrality by 2050 (U.S. Dairy, 2020). The United States passed the Methane Emissions Reduction Action Plan, and the U.S. Natural Resources and Conservation Service released an initiative to incentivize the reduction of GHG emissions in U.S. agriculture (The White House Office of Domestic Climate Policy, 2021; Natural Resources and Conservation Service, 2023). These build on the 2010 and 2021 Food and Agriculture Organization’s (FAO) climate-smart agriculture plans to assure better nutrition, a better environment, and a better life, leaving no one behind by using technology, innovation, and data. Climate-smart agriculture is an approach that helps guide actions to transform agri-food systems toward green and climate-resilient practices (Food and Agriculture Organization of the United Nations, 2010; 2021).

Anaerobic digestion (AD) is an important technology because it addresses the significant methane emissions from manure and can integrate well with the increasing number of large dairies that handle manure in liquid form (Beck et al., Reference Beck2023). AD is currently cited as the most effective technology for reducing methane emissions from manure, with dairies hosting 80% of on-farm AD systems (Manning and Hadrich, Reference Manning and Hadrich2015; Aguirre-Villegas and Larson, Reference Aguirre-Villegas and Larson2017; Wattiaux et al., Reference Wattiaux2019; United States Environmental Protection Agency, 2024). AD systems use bacteria in an oxygen-deprived environment to break down manure and capture the methane-rich biogas generated (United States Environmental Protection Agency, 2019). Biogas produced from AD can supply on-farm energy or be sold to electric grids or renewable natural gas systems. Beyond being an energy source, the digestion process reduces the pathogen load in the manure, improves wastewater quality, and converts manure into additional value-added products, including animal bedding and compost (Pagliano et al., Reference Pagliano2020; Ortiz-Liébana et al., Reference Ortiz-Liébana2023).

After AD extracts much of the methane, the remaining digestate is often stored in open systems. Ongoing research is investigating how to improve digestate management using technologies that build on AD systems to produce value-added products from the digestate, including biochar, hydrochar, and bioplastics (i.e., polyhydroxyalkanoates) using processes such as pyrolysis and hydrolysis (Monlau et al., Reference Monlau2016; Guillen et al., Reference Guillen2018; Lauer et al., Reference Lauer2018; Pagliano et al., Reference Pagliano2020; Struhs et al., Reference Struhs2020; Belete et al., Reference Belete2021; Tayibi et al., Reference Tayibi2021; Cui and Shah, Reference Cui and Shah2022; Lefebvre et al., Reference Lefebvre2023; Lim et al., Reference Lim2023; Ortiz-Liébana et al., Reference Ortiz-Liébana2023). We refer to these technologies as AD+. Stacking AD with AD+ systems may further improve effluent water quality and support the development of a circular economy for dairy manure management, soil enhancement, and value-added products for the system operator to use or sell (Guillen et al., Reference Guillen2018). Table 1 outlines AD and AD+ manure management innovations and associated value-added products considered in this study.

Table 1. AD and AD+ manure management process, inputs, and value-added products

To increase the prospects for the adoption of AD+ technologies, it is important to understand the characteristics of AD adoption on farms and perceptions of AD+ technologies as additional manure management strategies. Our study focuses on the Idaho dairy industry. We interviewed 21 professionals representing the farming community, government, nongovernmental organizations, and other professionals in the community to learn about their experiences with AD and perspectives about AD+ technologies designed to create additional value for dairy producers while mitigating negative environmental impacts from dairy waste.

Technology adoption

Studies related to the adoption of environmental, ‘green,’ and sustainable agricultural technologies developed significantly beginning in the 1990s focused primarily on physical and operational aspects of the technologies (Rennings, Reference Rennings2000; Jänicke, Reference Jänicke2008; Montalvo, Reference Montalvo2008; Schiederig, Tietze and Herstatt, Reference Schiederig, Tietze and Herstatt2012). We consider the diffusion of AD and AD+ technologies in the context of managing dairy manure waste. These include cutting methane leaks, protecting workers and communities, and maintaining and creating high-quality jobs. Combined with FAO’s concept of food security and better lives and environments, the diffusion of these technologies goes beyond understanding technical aspects (Food and Agriculture Organization of the United Nations, 2009; The White House Office of Domestic Climate Policy, 2021).

Specific to AD technology, the literature has also primarily focused on technical details, often overlooking other adoption drivers (Morse, Guthrie and Mutters, Reference Morse, Guthrie and Mutters1996; Pannell et al., Reference Pannell2006; Geels and Schot, Reference Geels and Schot2007; Montalvo, Reference Montalvo2008; Welsh et al., Reference Welsh2010; von Keyserlingk et al., Reference von Keyserlingk2013; Latawiec et al., Reference Latawiec2017; Sam, Bi and Farnsworth, Reference Sam, Bi and Farnsworth2017; Niles et al., Reference Niles2019; Traub et al., Reference Traub2021). Economic barriers have been mentioned in the literature and include high upfront capital costs and long payback periods (Morse, Guthrie and Mutters, Reference Morse, Guthrie and Mutters1996; Swindal, Gillespie and Welsh, Reference Swindal, Gillespie and Welsh2010; Welsh et al., Reference Welsh2010; Tranter et al., Reference Tranter2011; Manning and Hadrich, Reference Manning and Hadrich2015; Bangalore, Hochman and Zilberman, Reference Bangalore, Hochman and Zilberman2016; Hou et al., Reference Hou2018). Other factors include environmental beliefs, and peer group values and influence (Stephenson, Reference Stephenson2003; Bishop, Shumway and Wandschneider, Reference Bishop, Shumway and Wandschneider2010; Cowley and Wade Brorsen, Reference Cowley and Wade Brorsen2018).

We begin with the foundation of Rogers’ (Reference Rogers1962) diffusion of innovations (DOI) framework characterized by five factors associated with adoption: relative advantage, compatibility, simplicity/complexity, observability, and trialability. Relative advantage is the degree to which an innovation is seen as better than the technology it replaces. Compatibility is how consistent an innovation is with current systems and practices. Complexity refers to how difficult the innovation is to understand or use. Trialability is the extent to which an innovation can be tested or experimented with before a commitment to adopt it. Observability is the extent to which an innovation provides tangible results that can be seen in practice (Rogers, Reference Rogers1962; Reference Rogers2003).

While we use the DOI framework to help identify reasons for adoption, we also consider other adoption drivers less often included in the agricultural technology diffusion literature. Social and regulatory barriers to AD adoption are important drivers of adoption. Swindal, Gillespie, and Welsh (Reference Swindal, Gillespie and Welsh2010) and Welsh et al. (Reference Welsh2010) assert that states’ promotion of sustainable agricultural practices has generally relied on individualist appeals to private actors through free market environments, providing subsidies, and educating farm operators and not on appeals to public goods production. Bangalore et al. (Reference Bangalore, Hochman and Zilberman2016) reported that in the early 2000s, the United States lacked sufficient support for policies that incentivized fossil fuel alternatives. Others note that social costs such as odor annoyances to neighbors, animal and worker safety, ammonia emissions, concerns about increasing herd sizes to meet biogas production needs, producer values, and social injustice can hinder AD adoption (Krakat et al., Reference Krakat2017; Cowley and Wade Brorsen, Reference Cowley and Wade Brorsen2018; Beauchemin et al., Reference Beauchemin2022; Gittelson et al., Reference Gittelson2022; Lamolinara et al., Reference Lamolinara2022; Keough, Reference Keough2023). Figure 1 conceptualizes our approach. Understanding the current state of AD diffusion is critical to the adoption of future AD+ technologies.

Figure 1. Conceptual framework for the adoption of anaerobic digestion and diffusion of future innovations.

Materials and methods

The consolidation of the U.S. dairy industry has led to fewer but much larger dairy operations across the country, particularly in the leading dairy-producing states, including our study state of Idaho, the third-largest U.S. dairy-producing state (MacDonald, Law and Mosheim, Reference MacDonald, Law and Mosheim2020; Economic Research Service, 2024). AD shows promise for mitigating emissions on large dairy farms (>1,000 cows) (Aguirre-Villegas and Larson, Reference Aguirre-Villegas and Larson2017; Wattiaux et al., Reference Wattiaux2019). Idaho has 123 dairies with more than 1,000 dairy cows and another 43 with 500 or more dairy cows (USDA/NASS State Agriculture Overview for Idaho, 2022). Table 2 shows the rate at which the number of dairy farms and cows consolidated in Idaho from 2017 to 2022.

Table 2. Number of dairy farms and dairy cows (excluding calves) in Idaho, 2017–2022, and percent change (USDA NASS, 2022)

This study is part of a USDA Sustainable Agricultural Systems-funded project led by the University of Idaho to research how to create value-added products from dairy waste in a northern climate. Our study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board of the University of Idaho (Protocol No. 20-081) as exempt (Category 2). We conducted 21 qualitative, semi-structured interviews with 23 participants in 2021 (n = 12) and 2023 (n = 9). Participants were identified purposefully and through referrals to represent different perspectives in the dairy industry and the wider community. We had no prior relationships with any of the participants who were recruited through emails and follow-up calls. Informed consent was received from every participant. They included dairy farmers (n = 3); crop producers (n = 2); other organizations with dairy industry connections, including dairy nutritionists, a cattle veterinarian, industry advocates, and representatives of social service organizations (n = 6); environmental nongovernmental organizations (ENGO) (n = 5); government agency representatives (n = 3); and other non-profit or public organizations (n = 2). Two participants responded to recruitment but were unable to participate. Table 3 provides identification codes for each participant.

Table 3. Participant identification codes

Idaho hosts 11 of the 429 AD systems operating on dairies in the United States (Economic Research Service, 2023). Six systems were installed before 2013, and five after 2020 (Economic Research Service, 2023). Adoption in Idaho has been lower compared with other states with fewer larger dairies (>500 cows). For example, Michigan has 13, Pennsylvania has 29, and New York has 35 AD systems on dairies (Economic Research Service, 2023). Our study looks at a state with low adoption rates to better understand factors that facilitate or constrain adoption.

Interviews were semi-structured with open-ended questions, conducted by phone or online video calls, and lasted 25–75 minutes. The interview guide covered many topic areas, some of which go beyond this paper and were relevant to the larger USDA study. Related to the DOI, questions were asked about the observability of AD and AD+ technologies, familiarity with these technologies, their advantages/disadvantages, facilitators and barriers to adoption, and their impacts on farms and the broader community. We also asked about participants’ experience and roles in the dairy industry, their understanding of and questions about the proposed manure management strategies and resulting value-added products, and their attitudes toward adoption. Interviews included the researcher and the participant, were audio-recorded, and were conducted at a place and time of the participant’s convenience. We introduced the innovations described in Table 1 in an informational handout. The interview guide was updated in 2023 after the interviews were conducted in 2021.

Data collection and analysis followed a systematic approach to establish credibility, reliability, and transparency (Prokopy, Reference Prokopy2010; Elliott, Reference Elliott2018). Interviews were backed up by notes, transcribed, and then analyzed in the ATLAS.ti qualitative analysis software (Friese, Reference Friese2019). We developed an initial codebook by independently and inductively coding the first five transcripts. We established inter-rater reliability by coming together to compare and integrate our independent analyses into a single framework (Thomas, Reference Thomas2006; Elliott, Reference Elliott2018). Five researchers continued inductively coding transcripts, iteratively refining, and organizing codes into themes as we added new transcripts to the analysis (Elliott, Reference Elliott2018). Data collection ceased once we reached a point of saturation where no new information was occurring in the transcripts (Ritchie et al., Reference Ritchie2013). The research team met weekly throughout the data collection and analysis to discuss codes and themes and evaluate the credibility of findings and interpretations. We selected representative quotations from the data to present findings clearly and transparently, so the reader can interpret and evaluate the analysis themselves (Prokopy, Reference Prokopy2010). We presented preliminary results to a project stakeholder meeting in early 2024 where they provided feedback on the findings as a way of ground-truthing the results.

Results and discussion

Prior to asking specifically about AD and AD+, we led the semi-structured interviews with the open-ended question, “What do you see as the primary challenges for Idaho’s dairy industry as a whole?” Several themes emerged from this question alone: waste management, economic issues, environmental issues, and regulation. Table 4 displays these themes, representative quotes, and the type of participant who shared it.

Table 4. Dairy industry challenge themes

Waste management implicitly includes environmental components and was the more prevalent theme in participant responses. These themes provided a lead to investigating whether technology adoption also goes beyond physical and operational attributes of AD and AD+ and motivated the inclusion of environmental, economic, and regulatory issues. The next sections present results directly related to the diffusion of AD and AD+ technologies using Rogers’ (Reference Rogers1962; Reference Rogers2003) framework as a foundation and including other adoption drivers.

Adoption of anaerobic digesters

Observability and trialability

There was a priori reason to believe that the observability of AD systems in Idaho may be low, given the comparatively small numbers of installed systems in a large dairy state (Economic Research Service, 2023). However, most participants indicated familiarity with AD and often brought up the technology without prompts explicit to AD, as shown in Table 5. Participants who were furthest removed from the dairy industry were least familiar with AD technology. AD systems generally were observable, meaning the participants were aware of them. Without observability (awareness), barriers are created to trialability.

Table 5. Anaerobic digester observability and trialability themes

Aspects of trialability as seen in Table 5 do go beyond the physical attributes of AD and are related to economics, environment, and regulation in our qualitative sample. Operational issues directly tied to the technology represented only one aspect of trialability and were mentioned by a minority of participants. The economic aspects of installing a digester were most frequently mentioned. Environmental and regulatory aspects were mentioned less frequently.

Relative advantage/disadvantage

We identified seven themes related to the relative advantage of AD and the lack thereof. Two relative advantages commonly described by interviewees included methane reduction and the possibility of ancillary advantages to farmers through decreasing costs and producing value-added products. A community advantage mentioned was enhanced water quality. Themes related to the absence of relative advantage included the dependability of current systems, cost versus benefits, advantages that may not be reached in a cold climate, a lack of realized added value, and an incompleteness in addressing digestate. The costs that inhibit the trialability of AD systems also appear in this section as they were mentioned as a relative disadvantage in addition to hindering trialability. Participants also compared AD to alternative waste management technologies, noting that the advantages of AD may not surpass those of other alternatives or current practices, given the upfront investment required. Values were a subtheme. Thus, technological aspects of adoption are prevalent in participant responses, but responses go beyond these aspects and touch on the environment, economics, and community. Three participants had more to share about relative advantages and disadvantages: D3, P3, and P12. These participants were more knowledgeable of manure waste issues and readily shared their experiences and perspectives. Table 6 displays representative quotes about relative advantages and disadvantages.

Table 6. Relative advantages and disadvantages of anaerobic digester themes

Simplicity/complexity and compatibility

Participants had less to say about simplicity/complexity and compatibility compared with relative advantage. Table 7 displays representative quotes. The comments went beyond the technical aspects of adoption. Two themes emerged regarding the diffusion characteristics of (in)compatibility and complexity. Subthemes within compatibility touched on the technical aspect of difficulty in changing current manure management systems and the skill and time necessary to manage working digesters. Participants noted that investments have already been made in simpler systems that work. Another subtheme relates to the environmental impacts of producing a product (fertilizer) with nonstandard proportions of nutrients. Incompatibility with values, including ethics and the environment, was mentioned. Lastly, the number of cows needed to support a digester is related to economic and operational factors. Regulations are seen by some as cumbersome and time-consuming. The burden of regulation was brought up in the broader realm of challenges facing the dairy industry and was not limited to the regulatory burdens of AD.

Table 7. Anaerobic digester simplicity/complexity and compatibility themes

We now turn to newer and emerging AD+ technologies.

Perceptions of AD+ technologies

Before we moved to the specifics of biochar, hydrochar, and bioplastics, participants commented about newer AD+ technologies in general. Table 8 summarizes these comments. Themes include the general aspects of diffusion, including observability (awareness), relative advantage, and community impact. Responses were spotty; however, a few participants offered general comments about newer AD+ technologies.

Table 8. General themes about AD+ technologies

Biochar and hydrochar

While biochar has been known as a soil amendment for over 2,000 years, its use has only recently been ‘rediscovered’ as a method to improve carbon sequestration in U.S. agriculture (Mylavarapu, Nair and Morgan, Reference Mylavarapu, Nair and Morgan2013). Biochar is expected to improve agricultural yields and enhance the efficiency of AD systems (Latawiec et al., Reference Latawiec2017; Babaei and Shayegan, Reference Babaei and Shayegan2019; Mylavarapu, Nair and Morgan, Reference Mylavarapu, Nair and Morgan2013). Hydrochar can be produced from dairy manure with an uptake of up to 90% of the phosphorus. Thus, it can be used to recycle nutrients to be used as fertilizer (Wu et al., Reference Wu2017).

Observability and trialability

As new innovations in the United States, both observability and trialability are nascent in our sample, but a few participants indicated that they knew about biochar or hydrochar production or use. Two themes related to trialability include the environment and economics. Representative quotes are provided in Table 9.

Table 9. Observability and trialability related to biochar and hydrochar themes

Relative advantage

Overall, participants generally believed that there are or will be relative advantages to AD+ technologies and expressed cautious optimism about the possibilities for biochar or hydrochar. Themes related to relative advantage include operational advantages, including fewer weeds, the concentration of nutrients that decrease trucking costs (economics), and management efficiencies, as displayed in Table 10. These fit with the traditional DOI technical advantages. That said, they also implicitly incorporate economics and the environment. Therefore, it is difficult to separate advantages into discrete categories. Many responses relayed relative disadvantages related to economics, performance, a lack of proof of concept, and even the possible futility of researching biochar. Some participants communicated both advantages and disadvantages (P5 and P7). This is perhaps related to a lack of proof of concept as described below.

Table 10. Relative advantages and disadvantages of biochar and hydrochar themes

Simplicity/complexity and compatibility

One theme that emerged in the area of simplicity/complexity related to a lack of proof of concept and the need for more information. This theme goes beyond just the technology involved. More research and testing are needed before producers adopt technology to produce biochar and hydrochar. Themes related to compatibility and (in)compatibility included the ability to use current systems with biochar and the need to invest in an (AD) digester to obtain the additional benefits of AD+ technology. Dairy producer participants were more hopeful compared with other participants regarding both operational and economic factors. Because of the nascent features of biochar and hydrochar, the concepts of simplicity/complexity and compatibility were less frequently mentioned by participants. Representative quotes are displayed in Table 11.

Table 11. Simplicity/complexity and compatibility biochar and hydrochar themes

Bioplastics

Because the production of bioplastics from AD digestate is a future technology, participants expressed a limited but curious understanding of bioplastic production from dairy manure. They were both skeptical and optimistic about their potential. As with biochar and hydrochar, participant comments addressed the end product and not the AD+ technology, which is not currently commercially available.

Observability and trialability

Given the lack of commercial availability of the product and process, bioplastics are neither observable nor can our participants in Idaho actually sample the process or output. The overall theme is that participants are not widely aware of bioplastics produced from dairy manure, and there is no trialability until the technical processes are made available. Few participants had heard of them explicitly, “Yeah, I think so. I’ve heard of the bioplastics before, that’s come up before” (P3—Cattle nutritionist) and “Very, very tangentially. I wouldn’t want to be quoted on saying I know anything about them” (P11—Government agency). Participants were provided with an informational sheet to which they referred when addressing diffusion of bioplastics.

Relative advantages and disadvantages

Participants provided their opinions on the advantages and disadvantages of bioplastics. They commonly questioned the uses of bioplastics and whether there would be markets for the products. The themes that emerged included new product development, product demand, safety, and environmental impacts. Participants had many ideas about new products. They believed that the most promising are agricultural and industrial applications as opposed to human food storage. If there is no market, then producing bioplastics from dairy manure is not viable. Many thought immediately that the consumer market would be difficult, but the industrial market could be viable. A community-related theme was that if bioplastics are simply a ‘greenwashing’ escapade, the dairy industry’s reputation could be damaged. Some comments crossed the issues of new product development, economics, community (development), and the environment. Table 12 displays representative quotes.

Table 12. Relative advantages and disadvantages of bioplastics themes

Simplicity/complexity and compatibility

Participants were generally unfamiliar with the complexity of producing bioplastics, but several commented on this or had questions. Some questioned whether current manufacturing plants could use bioplastic inputs from manure. Because of the nascent nature of bioplastics, many fewer comments were made compared with the discussions of the relative advantages and disadvantages of AD technology. The two themes of operational complexity and compatibility are general and relate directly to Rogers’ (Reference Rogers1962; Reference Rogers2003) DOI approach. Another theme related to complexity is the need for more information. Table 13 displays representative quotes.

Table 13. Complexity and compatibility of bioplastics themes

Discussion and conclusions

Participant experiences with AD give indications that it will be important to show people the end products, their properties, and product uses before many farmers would consider upgrading an AD system to include the AD+ technologies of biochar, hydrochar, and bioplastic production. Participants were more familiar with AD compared with AD+ technologies, but in general, they could provide commentary on both the relative advantages and disadvantages of the potential new products.

Participants in this study were aware of the negative environmental impacts associated with large amounts of dairy waste. They were most familiar with AD and provided insights into why Idaho has not adopted more AD systems to address dairy manure waste, even though Idaho is the third-largest U.S. dairy state. Therefore, it was difficult for people to observe AD in action and to believe that AD+ systems could yield benefits. In general, participants with AD experience shared that current systems did not perform in a manner that justified the investment costs and required management that stretched already busy farmers. They also believed that income that could be generated from the production of methane currently does not surpass costs and that investment from the private and government sectors is insufficient to induce adoption. Further, questions about the return on investment for AD systems and AD+ technologies remain. These include questions about compatibility with current manure management strategies and the income they might generate. Participants also disliked that the regulatory burden added time costs to adoption.

Regarding AD+ advances, including biochar, hydrochar, and bioplastics, participants had several questions that need to be answered, including about the market for the products, whether these products are truly better than the status quo, if the income generated would be sufficient to justify the costs, and if the technologies just ‘juggle’ the unwanted nutrients instead of mitigating them.

There were also positives. Participants saw the advantages of AD and AD+ technologies in terms of manure management and the production of value-added soil amendments, biogas, and bioplastics, but they did not believe that these positives with regard to AD have been realized on farms or in the marketplace. Despite this general skepticism, most participants valued the potential benefits of AD and AD+ systems if they can cost-effectively meet the challenges of adoption in Idaho.

It is clear that AD adoption criteria continue to include both technological and economic aspects of diffusion theory as found in much of the literature (Morse, Guthrie and Mutters, Reference Morse, Guthrie and Mutters1996; Pannell et al., Reference Pannell2006; Geels and Schot, Reference Geels and Schot2007; Montalvo, Reference Montalvo2008; Swindal, Gillespie and Welsh, Reference Swindal, Gillespie and Welsh2010; Welsh et al., Reference Welsh2010; Tranter et al., Reference Tranter2011; von Keyserlingk et al., Reference von Keyserlingk2013; Bangalore, Hochman and Zilberman, Reference Bangalore, Hochman and Zilberman2016; Latawiec et al., Reference Latawiec2017; Sam, Bi and Farnsworth, Reference Sam, Bi and Farnsworth2017; Hou et al., Reference Hou2018; Niles et al., Reference Niles2019; Traub et al., Reference Traub2021). However, given the age of much of the literature, it seems that many of the same obstacles and facilitators of AD adoption remain that will be important to consider in the adoption of AD+ technologies.

It is also clear from our research that adoption characteristics go beyond technological and operational characteristics, and other considerations are important as AD+ technologies are developed. Environmental and social concepts are less common in the literature and should continue to be included in the agricultural technology diffusion literature (Swindal, Gillespie and Welsh, Reference Swindal, Gillespie and Welsh2010; Welsh et al., Reference Welsh2010; Krakat et al., Reference Krakat2017; Beauchemin et al., Reference Beauchemin2022; Gittelson et al., Reference Gittelson2022; Lamolinara et al., Reference Lamolinara2022; Keough, Reference Keough2023).

Suggestions for improving adoption include research that provides proof of concept for AD+ technologies; setting up demonstration sites where people can observe the technologies at work; providing evidence of markets for the outputs of the technology, including methane, soil amendments, and bioplastics; providing a path for transition to the use of new systems compatible and proven superior to current practices; and easing or helping adopters navigate the regulatory burdens associated with new technologies. Since AD+ adoption requires AD systems, further adoption of AD is a prerequisite for widespread adoption of AD+ systems, Even if AD+ technologies are proven to be advantageous, their adoption will take place in an area skeptical and cautious based on their experience with AD systems. This points to a need for substantial communication about how these systems work, what has changed to make them more viable in Idaho, and the benefits and tradeoffs of their use, including technological, economic, and social factors.

This study is based on qualitative methods and includes interviews with dairy producers and other participants in Idaho representing a wide range of for-profit, not-for-profit, and governmental organizations representing dairy producers and closely allied industries, environmental organizations, regulatory agencies, and those living in and serving the dairy community but removed from the dairy industry. As such, a wide variety of input was obtained in a state with low AD adoption considering the size of its dairy industry. However, the results cannot be generalized and therefore caution should be used in extrapolating these results to other states or other agricultural commodities. That said, this study represents a research-based approach to understanding local factors necessary to improve the effectiveness of the adoption of new agricultural technologies. As seen in this study, technology adoption goes beyond the technical and operational aspects of newly introduced technologies. Context is also critical as are regulatory, community, economic, and environmental considerations.

Acknowledgements

The authors would like to acknowledge Christy Dearien, Jeff Sellen, and Alex Radakovich for their contributions to this project.

Author contribution

Conceptualization: H.L.S., J.K., D.S., and S.N.; Formal analysis: H.L.S., D.S., J.K., and S.N.; Funding acquisition: D.S.; Investigation: H.L.S., S.N., and D.S.; Methodology: H.L.S., S.N., and D.S.; Project administration: D.S. and S.N.; Revision: J.K., M.T., and S.N.; Visualization: J.K., H.L.S., S.N., and A.R.; Writing—original draft: H.L.S. and J.K.; Writing—review and editing: J.K., S.N., D.S., H.L.S., and M.T.

Funding statement

This research was supported by a USDA Sustainable Agricultural Systems grant USDA 2020-69012-31871 from the U.S. Department of Agriculture’s National Institute of Food and Agriculture.

Competing interests

The authors declare no competing interests.

Ethical standard

The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board of the University of Idaho (Protocol No. 20-081, approved on 21 May 2020) as exempt (Category 2).

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Figure 0

Table 1. AD and AD+ manure management process, inputs, and value-added products

Figure 1

Figure 1. Conceptual framework for the adoption of anaerobic digestion and diffusion of future innovations.

Figure 2

Table 2. Number of dairy farms and dairy cows (excluding calves) in Idaho, 2017–2022, and percent change (USDA NASS, 2022)

Figure 3

Table 3. Participant identification codes

Figure 4

Table 4. Dairy industry challenge themes

Figure 5

Table 5. Anaerobic digester observability and trialability themes

Figure 6

Table 6. Relative advantages and disadvantages of anaerobic digester themes

Figure 7

Table 7. Anaerobic digester simplicity/complexity and compatibility themes

Figure 8

Table 8. General themes about AD+ technologies

Figure 9

Table 9. Observability and trialability related to biochar and hydrochar themes

Figure 10

Table 10. Relative advantages and disadvantages of biochar and hydrochar themes

Figure 11

Table 11. Simplicity/complexity and compatibility biochar and hydrochar themes

Figure 12

Table 12. Relative advantages and disadvantages of bioplastics themes

Figure 13

Table 13. Complexity and compatibility of bioplastics themes